Using 400 Hz in aviation power results in transformers and motors that are:

• A. Lighter and smaller for the same power rating.
• B. Less expensive but heavier.
• C. Less efficient but more robust.
• D. Only used for backup systems.

Answer: (A)

Higher frequency allows the magnetic components to be smaller and lighter for the same power. In a transformer, the voltage-to-flux relationship means you need fewer turns at 400 Hz than at lower frequencies, so the windings are shorter and the core can be smaller while avoiding saturation. Less material in both the iron core and copper windings translates directly to lighter, more compact equipment. The same idea applies to motors: higher frequency enables higher speed with smaller, lighter windings and core, maintaining the same power output. That weight and size savings is why aviation uses 400 Hz systems.